FIG. 1 depicts a conventional method 10 for fabricating a waveguide in a conventional energy assisted magnetic recording (EAMR) head. The conventional method 10 typically commences after a layer of optical material, such as Ta2O5, has been deposited for the waveguide core. A conventional mask structure is provided for the waveguide, via step 12. Step 12 typically includes providing a multilayer mask consisting of a planarization stop layer and a hard mask layer. This mask is provided by depositing these hard mask layers, using photolithography to form a photoresist mask having the desired pattern for the waveguide, then transferring the photoresist pattern to the hard mask. The pattern in the hard mask is then transferred to the core material, via step 14. The region around the core is refilled, via step 16. The refill typically includes depositing a dielectric, such as aluminum oxide, that is used for the cladding. The transducer is then planarized, via step 18. For example, a chemical mechanical planarization (CMP) may be used. The stop layer of the hard mask is typically a stop layer for the CMP. The CMP thus removes the portion of the cladding material above the core layer.
Although the conventional method 10 functions, performance and manufacturability of the conventional EAMR head may suffer. For example, FIGS. 2-3 depict conventional EAMR transducers 50 and 50′, respectively, after fabrication using the method 10. For simplicity, FIGS. 2-3 are not to scale and not all components are shown. The conventional transducer 50 includes waveguide 52 and test structures 60 and 70. The waveguide 52 is a tapered waveguide including a wider end portion 54, tapered region 56 and narrow region 58. The wider end portion 54 may be on the order of 5 microns, while the narrow portion 58 may be on the order of 0.5 micron. The text structures 60 and 70 are used in testing the performance of the EAMR transducer 50. The widest portions of the test structures 60 and 70 may be even wider than the waveguide 52. For example, the test structures 60 and 70 may be up to seventy microns in width. The EAMR transducer 50′ depicted in FIG. 3 is analogous to that depicted in FIG. 2. Similar components have analogous labels. Thus, the EAMR transducer 50′ includes waveguide 52′ having portions 54′, 56′, and 58′ as well as test structures 60′ and 70 corresponding to waveguide 52 having portions 54, 56, and 58 as well as test structures 60 and 70, respectively.
For the EAMR transducer 50 depicted in FIG. 2, the planarization step 18 of the method 10 is carried out until the narrow portion 58 of the waveguide 52 is exposed. As a result, wider portions of the waveguide 52 and test structures 60 and 70 may not be exposed. Instead, such portions of the waveguide 52 and test structures 60 and 70 may remain covered in the cladding material deposited in step 16. Such covered portions of the waveguide 50 and test structures 60 and 70 are denoted by the dashed lines in FIG. 2. In contrast, for the EAMR transducer 50′ of FIG. 3, the planarization step 18 is carried out until the wider portions of the waveguide 52′ and test structures 60′ and 70′ are exposed in step 18. However, this may result in overpolishing of the narrow portion 58′ of the waveguide 52′. Thus, the core materials for the waveguide 52′ may be partially or completely removed. In either case, fabrication and performance of the conventional EAMR transducers 50 and 50′ are adversely affected.
Accordingly, what is needed is a system and method for improving manufacturability and performance of an EAMR head.